PHYTOPHTHORA-IRANICA, A NEW ROOT PATHOGEN OF MYRTLE FROM ITALY

A homothallic Phytophthora sp. producing persistent and markedly papillate sporangia was isolated, together with P. nicotianae, from the rotted roots of seedlings of myrtle (Myrtus communis), grown in pots in a commercial nursery in Sardinia, Italy. The homothallic species isolated from myrtle was identified as P. iranica on the basis of morphological and cultural characteristics; it differed from other known Phytophthora spp. belonging to Waterhouse's group I in its higher cardinal growth temperatures. In addition, the isolate of P. iranica from myrtle was distinguished from P. cactorum by the electrophoretic protein pattern and the serological reaction of mycelial extracts, from P. clandestina by its simple antheridia and the absence of a prominent basal plug in the sporangia, and from both P. cactorum and P. clandestina by its persistent sporangia. In pathogenicity tests, P. iranica proved to be nonpathogenic to wound-inoculated potato tubers, less pathogenic than P. nicotianae to apple fruit, and only weakly pathogenic on tomato seedlings or the stem and roots of myrtle seedlings. This is the only record of P. iranica outside Iran.